1. Field of the Invention
The invention relates generally to a dentifrice composition containing reactive ingredients and more particularly to a dentifrice composition improved storage stability containing reactive peroxide and bicarbonate ingredients.
2. The Prior Art
It has been found to be very desirable to incorporate peroxide compounds in dentifrice compositions, the efficacy of peroxide compounds in oral hygiene having long been recognized. Such compounds have been proven effective in the treatment of gingivitis, periodontitis and in combating plaque. Additionally, peroxide compounds have been utilized for oral cosmetic purposes such as tooth whitening which results from bleaching and cleansing of tooth surfaces. A problem encountered with dentifrices formulated with peroxide compounds, is that the peroxide compounds tend to exhibit undesirable stability and decompose when subjected to a storage environment of abnormally high temperature e.g., temperatures in excess of 100.degree. F.
This problem is exascerbated when peroxide compounds are utilized in combination with other ingredients of dentifrices which are reactive including alkaline abrasive agents such as sodium bicarbonate. The tendency of peroxide compounds to react with such other ingredients presents significant stability problems with respect to providing products which achieve adequate shelf life. Due to such instability the presence of the reactive ingredients causes gasing and bloating of the containers in which the dentifrice product is stored occur rendering the dentifrice product unacceptable for consumer use.
Examples of prior art attempts at providing stable peroxide containing dentifrices in which a second reactive ingredient is also included are found in the disclosures of U.S. Pat. No. 4,971,782, U.S. Pat. No. 4,897,258 and U.S. Pat. No. 4,837,008.
U.S. Pat. No. 4,837,008 discloses an aqueous dentifrice containing a peroxide and/or bicarbonate ingredient in which the ingredients are provided with a barrier coating to prevent reaction of the ingredients. A disadvantage to such dentifrice is that release of the ingredients for cleaning effect during use is diminished by the presence of the barrier coating.
U.S. Pat. No. 4,897,258 discloses an anhydrous dentifrice containing calcium peroxide and sodium bicarbonate wherein the anhydrous state of the dentifrice prevents reaction between the ingredients. A disadvantage to such dentifrice is that in spite of the anhydrous state of the dentifrice, limited storage stability is experienced.
U.S. Pat. No. 4,971,782 discloses an anhydrous dentifrice containing peroxide and bicarbonate ingredients in which one of the ingredients is coated with a water dissolvable coating and a peroxide stabilizer is included in the dentifrice to further enhance storage stability. In spite of the presence of the stabilizer, the dentifrice remains deficient in storage stability required for commercial use.
Because of the storage stability problems with dentifrices containing reactive ingredients such as peroxides and bicarbonate compounds, dentifrices containing either the peroxide or bicarbonate compound are separately maintained before use. For example, U.S. Pat. No. 4,687,663 discloses placing each of a peroxide gel and bicarbonate paste into separate compartments of a single two compartment container to avoid interaction between these ingredients before use. Such dual packaging devices are costly to manufacture and attempts at simultaneous even delivery of the two separate dentifrice components from the dual compartmented device is many times erratic.
There is therefore a need in the art for a dentifrice containing peroxide and other reactive ingredients such as bicarbonate salts which dentifrice remains stable during storage for extended periods of time and can be stored without provision for costly physical separation of components.